The present invention relates to an automobile security system, and more particularly, to a key assembly for use in a vehicle ignition and lock unit.
Various types of security systems used in conjunction with the ignition circuit of a vehicle are known in the art. Many of these systems include anti-theft and/or anti-tampering mechanisms which are incorporated to deter the unauthorized use of vehicles. An electronic vehicle ignition lock is a component of some of these systems which can increase vehicle security and even lower insurance rates in some countries.
An electronic interlock system uses a coded activation signal which enables a vehicle operator to run a vehicle. Coded activation signals are generally read electronically within an ignition lock and subsequently sent to an electronic control module. The electronic control module controls engine operation and enables the vehicle to run only if the correct activation signal is received. Therefore, an electronic interlock system prevents a vehicle from running even if the ignition lock is bypassed or pulled. This system makes vehicle theft more difficult and time consuming.
The ignition keys employed for use with electronic interlock systems traditionally contain mechanical and/or electronic interlock codes. One such system incorporates a resistor pellet in the ignition key. The resistor pellet provides a resistor of a resistance such that when the ignition key is inserted into and rotated within a vehicle's ignition cylinder unit, an electrical current is applied through the resistor. A decoding circuit determines if the resistance of the resistor pellet in the ignition key is within a predetermined resistance “window.” If the resistance provided by the resistor pellet in the ignition key is within the predetermined resistance range, the vehicle will run. To the contrary, if the resistance falls outside of the predetermined resistance window, the vehicle will not run. Examples of these interlock systems and associated keys are illustrated in U.S. Pat. Nos. 4,250,482, 5,083,362 and 5,156,032.
In another electronic interlock system, radio frequency identification (RFID) is used in the enabling or disabling of engine operation. An RFID interlock system consists of a reader which sends a signal to an antenna associated with a transponder that is mounted in a key. The transponder includes a transponder circuit, which can comprise an integrated circuit or discrete components, and a resonant circuit formed by a capacitor and an inductor or coil. The signal energizes the transponder, and the transponder responsively transmits a unique identification code back to the reader which decodes the identification code. If the signal transmitted by the transponder represents a valid identification code, the reader transmits this information to the vehicle's electronic control module thereby enabling engine operation. However, if the signal is not a valid identification code, the reader causes the electronic control module to prevent engine operation. Typically, the antenna associated with the transponder produces a relatively high energy electromagnetic field which is coupled to the coil of the transponder and converted to a DC voltage which is used to power the electronic circuits of the transponder. The transponder transmits its unique identification code in the form of a low energy radio frequency signal that is received and decoded by the reader as described above.
Precisely because RFID electronic interlock systems are such effective security devices, it is critical that these systems work dependably in all the conditions a vehicle might encounter. The result of an RFID system failure is that a vehicle owner, or other person properly in possession of the keys for a given vehicle, is stranded and unable to bypass the interlock system to operate the vehicle. Electronic interlock systems are industry specified. Industry test configurations and requirements reflect conditions and circumstances which RFID interlock systems might actually encounter and, therefore, are a fairly reliable indicator of the dependability of the security systems.
Older RFID systems used transponder chips that are packaged in glass vials, often containing silicone, in an effort to protect the electronic components contained within the vials. Developments in the electronic industry have resulted in transponders that are overmolded with plastic and such transponders have gained wide acceptance in RFID interlock systems for vehicles. Recently, the inventors have discovered that harsh operating conditions affect the performance of RFID interlock systems in which the transponders are packaged in plastic material. However, RFID systems employing such transponders molded in key heads meet industry requirements, only when used with relatively expensive receivers.
One of the most popular configurations of transponders currently available is produced by Texas Instruments, Inc., as Texas Instruments, Inc. part number RI-TRP-W9WK. Another popular transponder configuration is that manufactured by Motorola, as Motorola part no. 05504-001. Both transponders include an overmold of a plastic material with electronic components located substantially within the overmold.